White is the only colour you can’t reach by mixing together other coloured paints, you have to begin with a special white pigment. When coloured lights are mixed together, it is called additive mixing. Red, green and blue are the primary colours for additive mixing. If all of these colours of light are shone onto a screen at the same time, you will see white. Sir Issac Newton was the first to prove that white light is made up of all the colors that we can see using the prism experiment.